1. Field of the Invention
The present invention relates to a crosslinked polymer nanoparticle containing composition, a method for preparing a copolymer using the composition, and a vinyl chloride resin with improved foam molding properties comprising the same, and more particularly, to a crosslinked polymer nanoparticle containing composition capable of providing improved foam molding properties upon being added to a vinyl chloride resin (PVC), a method of preparing a copolymer using the composition, and a vinyl chloride resin with improved foam molding properties comprising the copolymer.
2. Description of the Related Art
Vinyl chloride resins that are polymers containing more than 50% of vinyl chloride have various applications due to its affordable, easy to control as hardness, and can be applied to most of the processing equipment. In addition, since they provide molded products having excellent physical and chemical properties, vinyl chloride resins have been widely used in various fields.
Such widely used vinyl chloride resins have several disadvantages in terms of impact strength, processibility, thermal stability, and thermal deformation temperature. Thus, additives have been developed to compensate these drawbacks. Additives such as impact modifiers, processing aids, stabilizers, fillers, and the like, were appropriately selected depending on the purpose and use thereof.
Recently, an attention has been increased to foam molding as a means to be lightweight and reduce prices of molded products. However, if it foam-molded vinyl chloride resins alone, it cannot have sufficient elongation and melt strength, so that the products have poor appearance, and cannot get low foaming magnification due to large size and non-uniform of foaming cell size. Thus, in order to complement these drawbacks, a method of adding a processing aid including methyl methacrylate as the main ingredient and a foaming agent to a vinyl chloride resin has been generally used.
U.S. Pat. No. 6,140,417 discloses a polymerization method of one compound selected from the group consisting of methyl methacrylate, alkyl acrylate, and alkyl methacrylate with a copolymerizable vinyl monomer in a three-stage process to improve processibility and foamability. The three-stage polymerization process comprises first stage polymerization of adjusting low glass transition temperature (Tg), second stage polymerization of adjusting the Tg higher than that of the first stage polymerization, and third stage polymerization of adjusting the Tg lower than that of the second stage polymerization.
In addition, U.S. Pat. No. 6,221,966 discloses a two-stage polymerization method to improve processibility, transparency, and foaming properties of the vinyl chloride resin, which decreases the size of the particle diameter, the outer layer of the two-stage has relatively higher glass transition temperature(Tg), and the inner layer has relatively lower glass transition temperature(Tg) of the two-stage by reducing the content of methyl methacrylate. However, this method provides insufficient processibility enhancement and uniformity of foamed cells.
U.S. Pat. No. 6,391,976 also discloses a method of adding a small amount of a processing aid consisting of methyl methacrylate and alkyl methacrylate having 3 to 5 of carbon number, however, the method does not meet processibility and foaming properties.